Decay scheme

Under the decay scheme of a radioactive nucleus is defined as a graphical representation of the energy correlations in the decay, which can sometimes be quite complicated. A simple example, the decay of radioactive cobalt isotope 60Co is to see here.

60Co decays by emission of an electron ( beta decay ) with a half-life of 5.26 years in an excited state of 60Ni, which passes through two gamma transitions very rapidly to the ground state.

It is useful to imagine the image in a coordinate system where the abscissa is the atomic number and the ordinate is the energy of the core states is applied. The arrows indicate the light emitted ( = emitted ) particles; vertical arrows mean gamma transitions, the oblique arrow a beta transition. When gamma transition Gamma energy is specified, the beta decay, the maximum energy of the emitted electrons. Gamma radiation is emitted mostly by beta decay, it is produced while almost immediately after the beta decay ( see exception below).

Nickel is the right of cobalt, because the atomic number of nickel to 1 is greater than that of cobalt: the atomic number increases in beta decay to 1 When a positron decay with decreasing atomic number, the inclined arrow would proceed from right to left, as in an alpha decay ( see below).

Since energy is conserved and the nuclear decay fly energetic particles, arrows can only run (vertical or oblique) from top to bottom.

A more complicated scheme is the decay of the isotope gold 198Au, obtained by neutron irradiation in the nuclear reactor by natural gold. 198Au decays by beta decay to excited states (or to the ground state ) of the mercury isotope 198Hg. On the mercury stands right next to gold, because gold is the atomic number 79, has mercury atomic number 80 The excited states decay after a very short time (2.5 and 23 ps; 1 picosecond is one trillionth of a second) also to the ground state.

While excited nuclear states are usually very short-lived and only as a successor of a beta decay (see above) occur, the excited state of the here shown right technetium isotope " metastable" (hence the " m" in 99mTc), that is, relatively durable. It decays by gamma radiation with a half-life of 6 hours.

Here is an alpha decay is now shown on the left, namely that of the discovered by Marie Curie, polonium element with mass number 210 The isotope 210Po is the penultimate member of the uranium - radium decay chain; it decays with a half-life of 138 days to a stable lead isotope. In almost all cases, the decay via emission of an alpha radiation of 5.305 MeV is done. Only in a case of 100,000 appears an alpha particle of lower energy; the decay leads to an excited state of 206Pb, the gamma radiation leads back to the ground state.

A decay scheme can also be much more complicated than those shown here. 20 or more possible states ( levels ) with a variety of possible transitions are not uncommon. The emitted gamma radiation then forms a spectrum with a corresponding number of different energies ( spectral lines ).